The present disclosure generally relates to a laser communication system, and specifically relates to a compact system for active co-boresight measurement used in a laser communication system.
Laser-based systems, such as laser communication systems, commonly employ multiple laser beams. A laser communication system can include two or more laser terminals (either stationary terminals or moving terminals) that communicate between each other by encoding information into laser beams. To exchange information data between two laser terminals of the laser communication system, each laser terminal transmits a laser beam with encoded data to another laser terminal and receives another beam with encoded data transmitted from the other laser terminal. In order to maximize communication performance of the laser communication system, a co-boresight angle between the transmission beam and the received beam needs to be within a specific threshold limit. A relative misalignment between communicated laser beams is typically measured using infrared cameras employed at each laser terminal of the laser communication system.
The conventional solution to this problem is to use some form of tracking to reject common-path disturbance, a separate mechanism to apply open-loop point-ahead, and careful opto-mechanical design techniques to minimize launch shift, jitter, and thermal drift effects that would otherwise contribute to misalignment between optical paths. Adjustment mechanisms are also built-in to the hardware design, which skilled engineers and technicians can use to achieve precision alignment during initial assembly. Unfortunately, this approach tends to drive up hardware complexity in the form of intricate mounting and adjustment features, tight machining tolerances, increased part quantity, and the use of exotic materials. Furthermore, the manual alignment process can be time-consuming and prone to quality issues, even for skilled engineers and technicians. For systems which require variable point-ahead, the point-ahead mechanism must make use of highly precise and repeatable position sensors, which can further increase cost and may even require their own calibration effort. The end result of this approach is a system that is very complex, and in turn, very expensive to produce.